This post is part of our live blog series from the Resilient Cities 2015 congress. For more live blogs, please click here.

You’re sat in a room at a university. The air conditioning is running at full throttle, and it’s so chilly that the students are wearing sweaters and scarves. Next door is a server station, where rows of computers are pumping out heat throughout the day. Does this seem like a missed opportunity to you?

It did to Anna Oursler, a graduate student at Columbia University, USA. In a session on “urban heat islands” – cities or metropolitan areas that are significantly warmer than the surrounding rural areas due to human activities – Oursler presented her research on what she calls “thermal mismatch”: situations where sources of heating and cooling are adjacent to each other but not linked.

The most common source of waste heat is air conditioning. The waste heat and the emissions from the energy production contribute to warming of the urban environment, increasing the need for air conditioning in a vicious circle.

Oursler’s research is being upscaled to the level of the city. It shows that privately-owned buildings and buildings on interior lots are most likely to have high-energy consumption. We should use this information in city planning, she argues, locating buildings with high energy demand and low energy demand next to each other. It is not possible to capture all waste heat, but, as Oursler said:

If we can find ways to reuse just a fraction of this waste heat, cities would decrease their energy consumption and reduce their dependence on fossil fuels.

The potential is significant: waste heat in New York is equivalent to 52% of the production of the city’s largest nuclear power plant. As other presenters at this session pointed out, other options are available for reducing the effect of urban heat islands. However, Oursler commented:

My position is that planting trees and painting roofs are solutions that simply won’t be sufficient.

Perhaps we therefore need more examples like that of Islington, London, which is proposing to use excess heat from underground trains to heat homes. However, we might wonder how feasible it is to plan cities in this way. Oursler’s proposal is not a radical solution, but it is more wide-ranging and theoretical than other solutions presented at this panel, and I would be interested to hear the views of city planners on this topic.